1. Field of Invention
The present invention relates to a torque-providing tool and, more particularly, to a torque-setting device for use in a torque-providing tool.
2. Related Prior Art
As disclosed in U.S. Pat. No. 6,334,377, an adjustable-torque wrench includes a shank 10, a head 11, a spring 15, a follower 13, a pin 14, a handle 20, a lock fastener 21, a lock nut 23, a control ferrule 30 and a knob 26. The head 11 is secured to an end of the shank 10. The spring 15 is located in the shank 10. A section of the follower 13 is located in the shank 10, against the spring 15. The pin 14 is driven in the follower 13 via a slot 12 defined in the shank 10. Thus, the section of the follower 13 is movably but not rotationally located in the shank 10. The follower 13 includes an extension 16 with a reduced diameter, thus forming a shoulder 17.
First and second threads are formed on an internal face of the handle 20. The first thread of the handle 20 is engaged with a thread 18 formed on the shank 10. The second thread of the handle 20 is engaged with a thread of the lock fastener 21. The thread of the lock fastener 21 is engaged with a thread of the lock nut 23. Thus, the handle 20, the lock fastener 21 and the lock nut 23 can only be rotated together. The extension 16 is inserted through an orifice 22 of the lock fastener 21. The shoulder 17 is located against the lock fastener 21. In use, the handle 20 is rotated around and hence moved along the shank 10 to make the lock fastener 21 push the follower 13. Hence, the follower 13 compresses the spring 15.
The control ferrule 30 is movably located between the handle 20 and the knob 26 that is secured to the extension 16 of the follower 13. In a position, teeth 31 formed on an internal face of the control ferrule 30 are engaged with teeth 24 formed on the handle 20 and teeth 28 formed on the knob 26. Thus, the handle 20 cannot be rotated relative to the knob 26, the follower 13 and the shank 10. Hence, torque cannot be adjusted. In another position, the teeth 31 of the control ferrule 30 are disengaged from the teeth 28 of the knob 26. Thus, the handle 20 can be rotated relative to the knob 26, the follower 13 and the shank 10. Therefore, torque can be adjusted.
As disclosed in co-pending U.S. patent application Ser. No. 12/434,662 filed by the present applicant, a torque-setting device includes a handle 10, a sleeve 15, a driving unit 11, a spring 20, a pusher, an axle 30, a knob 40 and a positioning unit 50. The sleeve 15 is attached to an end of the handle 10. The sleeve 15 includes grooves 18 defined in an internal face. The driving unit 11 is attached to an end of the handle 10 and connected to a strain gauge. The spring 20 is abutted against the strain gauge within the handle 10. The pushing element 33 is movably but not rotationally located in the handle and abutted against the spring 20.
The axle 30 includes a section rotationally but not movably located in the handle 10 and engaged with the pushing element 33. Thus, rotation of the axle 30 relative to the pushing element 33 causes movement of the pushing element 33 relative to the axle 30 and hence the spring 20 to set a value of torque.
The knob 40 is formed with a tooth 42. The knob 40 is connected to another section of the axle 30. The knob 40 is operable to rotate the axle 30 relative to the pushing element 33. The knob 40 is movable between a first position and a second position. In the first position, the tooth 42 is inserted in one of the grooves 18 of the handle 10 to retain the value of torque. In the second position, the tooth 42 is removed from the grooves 18 to allow the rotation of the knob 40.
The positioning unit 50 includes a lining 56 and a spring-biased detent assembly. The lining 56 is disposed in the knob 40 so that they cannot be rotated or moved relative to each other. The spring-biased detent assembly includes a spring 54 disposed in a recess 53 defined in the restraining element 36 and a detent 55 biased with the spring 54. The detent 55 is formed like a cap for receiving a section of the spring 54. The detent 55 is in contact with the internal side of the lining 56. The detent 55 can be located against the annular rib formed on an internal face of lining 56 to restrain the positioning unit 50 relative to the sleeve 15.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.